Sodium bicarbonate, baking soda, has been used for centuries as an aid to clean the human mouth and for the deodorizing and freshening the breath. In vitro scientific studies have shown that the bicarbonate ion has mild but significant antimicrobial properties against specific bacterial species, in particular anaerobic bacterial species, many of which have been shown to cause periodontal diseases (Newbrun E., et.al. J. Periodontal. 55, 11, 658-657, 1984). Compositions of baking soda and dilute hydrogen peroxide have been prescribed as a preventative and mild remedial treatment for gingivitis and periodontal diseases. (Randal, J. E., A. H. 2, 82--82, 1982, Rudy et al., U.S. Pat. No. 4,971,782). For example, the Keyes technique, named after Dr. Keyes from the National Institute of Health (NIH), is a common preventative and remedial treatment for mild to moderately severe cases of periodontitis. The Keyes technique can employ baking soda and dilute solutions of hydrogen peroxide. These agents are combined by simply dipping a toothbrush into a 1.5% to 3% hydrogen peroxide solution followed immediately by spreading the peroxide-wetted toothbrush through a bed of baking soda and applying it to the teeth with a brushing motion. A major shortcoming of this method is the foul taste, as well as the resultant gum irritation. Another Keyes method uses a thick paste made of baking soda powder in combination with 1.5% to 3% hydrogen peroxide. The paste is applied directly to the surface of the teeth and gums and maintained there for extended periods of time (on the order of a few minutes to less than an hour). However, laymen can have difficulty in preparing this paste and the compound gives rise to discomfort as a result of its foul taste and long residence time required to realize efficacy.
Many modern-age toothpaste compositions also use baking soda as the chief ingredient, presumably to add to the plaque reducing and breath deodorizing properties of the dentifrice. However, oral preparations containing the bicarbonate ion as the active component have heretofore not been demonstrated to have significant effectiveness, that is they have not been reported to show significant bactericidal properties in vivo.
Halitosis (oral malodor) has also been an unsolved physiological problem for centuries, and remains as such in the modern era. The chemical basis of halitosis lies in the concentration of mouth-bound volatile and odiferous compounds, primarily organic and inorganic sulfides as well as organic amines. These odiferous volatiles are biologically synthesized by particular microorganisms that reside in the oral cavity. Halitosis is primarily caused by certain anaerobic strains of bacteria (Rosemberg, M., Bad Breath: Research Perspectives, Ramot Publishing, 1995). Specifically, the proliferation in saliva of the anaerobic bacterial pathogen Fusobacterium Species, in combination with other anaerobes, have been shown as the major biological source of halitosis. Chemical mouthwash treatments have been recommended to treat halitosis, such as dilute solutions of chlorine dioxide, which presumably act as an oxidizing agent to rid of oral sulfides. A major shortcoming of this method is the unproven long term safety of the chlorine dioxide solution (bleach). Since a significant amount of the chlorine dioxide is absorbed through the mouth tissue and is sometimes ingested, implementation of the mouthwash into the daily practice raises serious questions of safety.
Effervescent oral compositions have been taught in several U.S. patents dating from about 1914 to the present. For example, U.S. Pat. No. 1,297,494 is directed to an effervescent, solid dentifrice comprising an acid salt and a bicarbonate salt which mutually react in the presence of moisture to produce CO.sub.2 and an initially weak acid solution which contacts the surface of the teeth. Howell, U.S. Pat. No. 3,962,417, teaches an effervescent dentifrice for treatment against caries. Yeh, U.S. Pat. No. 4,267,164 teaches an effervescent oral composition for the convenient and effective delivery of fluoride ion to the oral cavity. Welsh, U.S. Pat. No. 3,518,343 teaches an effervescent mouthwash tablet composition as a tablet form, where the binder is a specific combination of ingredients.
The prior art mentioned above teaches that combinations of baking soda and organic acids (typically fruit acids) begin to immediately effervesce when placed in the oral cavity, thereby chemomechanically removing plaque and food debris during effervescence.
Although bicarbonate based mouthwashes or solid dentifrice products have been taught, none have been demonstrated as bonafide in vivo bactericidal agents. Moreover, none have been proven to significantly effect an improvement to the health of the gingiva or for conditioning of the breath.
A further shortcoming of the prior art is the inherent instability of the effervescent compositions, since the self-sustaining effervescent reaction takes place rapidly with water thus causing commercial embodiments to be inherently unstable. This in turn results in the composition having an unacceptable shelf life unless it is prepared and securely packaged in an inert environment. Further, compositionally, the prior art compounds lack antimicrobial efficacy and have a poor taste, usually chalky or salty. The problems of developing a dentifrice which has both good taste and efficacy is crucial since frequent use of the composition is important to long term regulation of gingivitis and periodontitis. Finally, the plaque reducing properties of compositions in the prior art are minimal, since no plaque adsorption mechanism is provided.